Apparatus for automatically limiting the size of an x-ray beam in response to cassette size

ABSTRACT

The size of an X-ray beam is automatically adjusted in response to signals produced by a pair of continuously variable transducers, such as rotary potentiometers, mounted on a cassette holder. One of the transducers is preferably adjusted by a pivoted arm on the holder adapted to contact the side of a cassette positioned on the holder. The other transducer is preferably adjusted, through suitable gearing, by a cable connected to one of a pair of jaws which center the cassette on the holder. The preferred embodiment also has a switch and means to open the switch when there is no cassette on the holder in order to prevent the X-ray generator from being activated.

United States Patent 1 1 Lackey et al.

[ Oct. 9, 1973 [75 I Inventors: Ray R. Lackey, Madeira; Carold R.Henninger, Reading, both of Ohio [73] Assignee: Sybron Corporation,Rochester,

221 Filed: Nov. 26, 1971 121 Appl. No.: 202,334

Primary ExaminerArchie R. Borchelt Assistant ExaminerB. C. AndersonAttorney-Theodore B. Roessel [57] ABSTRACT The size of an X-ray beam isautomatically adjusted in response to signals produced by a pair ofcontinuously variable transducers, such as rotary potentiometers,mounted on a cassette holder. One of the transducers is preferablyadjusted by a pivoted arm on the holder adapted to contact the side of acassette positioned on the holder. The other transducer is preferablyadjusted, through suitable gearing, by a cable connected to one of apair of jaws which center the cassette on the holder. The preferredembodiment also has a switch and means to open the switch when there isno cassette on the holder in order to prevent the X-ray generator frombeing activated.

1] Claims, 4 Drawing Figures PATENTED 9 7 sum 1 nr 3 PATENTED DU 9 I975SHEET 2 BF 3 N UE APPARATUS FOR AUTOMATICALLY LIMITING THE SIZE OF ANX-RAY BEAM IN RESPONSE TO CASSETTE SIZE BACKGROUND OF THE INVENTION Thisinvention relates to X-ray apparatus and more particularly to apparatusfor automatically adjusting the size of an X-ray beam in response to thesize of the cassette in a cassette holder.

In the use of X-rays for medical diagnostic purposes, it is desirable tolimit the size of the X-ray beam to substantially the exact size of thefilm, paper, plate or other X-ray sensitive material being exposed inorder to minimize potential health hazards to the patient and fogging ofthe film or other sensitive material. In order to simplify thediagnostic procedure and to eliminate potential operator errors, it isalso desirable to have these size adjustments performed automatically bythe X-ray apparatus.

Systems for adjusting the size of an X-ray beam to correspond tostandard X-ray film cassette sizes are disclosed in US Pats. Nos.2,921,202-Brger et al., 3,502,878-Stewart et al., 3,518,435-Kok and3,581,094-Peyser et al. However, it would be desirable to have a systemwhich would automatically adjust the X-ray beam to correspond to anyX-ray cassette, standard or non-standard. Preferably, this system shouldalso minimize the number of connections to the cassette holder. The Kok,Stewart and Peyser et al. systems, which utilize a plurality of switchescorresponding to different cassette sizes, require a large number ofconnections between the cassette holder and the controls which adjustthe size of the X-ray beam. As a result either the cassette holder mustbe permanently attached to the rest of the system, or an electricalconnector with a large number of contacts must be employed.

SUMMARY OF THE INVENTION It is an object of this invention to provide asystem for sensing both the width and the length of a cassette that hassubstantially infinite resolution within a certain range of cassettesizes, i.e. which is continuously variable throughout the range ofsizes. With this system the size of an X-ray beam can be adjusted tocorrespond to any cassette, standard or nonstandard, within this sizerange.

Another object of this invention is to provide a system for adjustingthe size of an X-ray beam in response to the size of a cassette in aholder in which the number of connections between the cassette holderand the means for adjusting the size of the beam are minimized. As aresult, the components that sense the cassette size can be permanentlymounted on the cassette holder and the holder can be removed from thesystem without breaking a large number of connections.

Basically, this invention provides a cassette holder having a pair ofcontinuously variable transducers mounted thereon, means for adjustingthese transducers proportional to the width and the length of a cassettein the holder, and means to connect the transducers to apparatus foradjusting the size of an X-ray beam. Since the transducers arecontinuously variable, the size of the beam may be adjusted tocorrespond-to any size cassette, standard or nonstandard, within therange of cassette sizes the holder is designed to accommodate. Inaddition the use of continuously variable trans- '2 ducers minimizes thenumber of connections which must be made between the cassette holder andthe beam adjusting apparatus.

A still further object of our invention is to provide means forautomatically preventing operation of an X-ray system if a holderwithout a cassette in it is accidentally inserted in the system. This isaccomplished by mounting a switch on the holder and utilizing the widthsensing means to automatically open this switch if a holder withouta-cassette is inserted in the system.

Other objects and advantages of this invention will be apparent from thefollowing detailed description.

DRAWINGS DETAILED DESCRIPTION FIG. 1 illustrates an X-ray cassette trayor holder 10 adapted to be inserted in a Bucky diaphragm or similarcarriage in an X-ray diagnostic system such as an X-ray table. Theholder has front and rear centering jaws l1, 12 adapted to grip acassette 13 in which a film, paper, plate or similar sensitive materialis mounted. The jaws may be secured in place by a lock 14 attached tothe front jaw 11. The jaws and lock are disclosed in more detail in theco-pending application of Ray R. Lackey, Carold R. Henninger and HenryJ. Schneider, Ser. No. 202,335, filed Nov. 26, I971. The holder 10 alsohas a pivoted arm 15 adapted to contact the side of cassette 13, and acable 16 attached to the rear jaw 12. The pivoted arm and cable areconnected to transducers positioned beneath a cover 55 on the rear ofthe holder. In the illustrated embodiment the transducers, which areshown in FIGS. '3 and 4, are a pair of rotary potentiometers l7, 18. Ofcourse, rotary potentiometers, like a number of other transducers thatmight be used in this invention, are actually adjusted in a series ofvery small steps. Thus, strictly speaking they are not continuouslyvariable. However, the individual adjusting steps of typical rotarypotentiometers are so small that, for the purposes of adjusting the sizeof an X-ray beam, these potentiometers can be considered to becontinuously variable.

Referring to FIGS. 2 and 3, arm 15 is pivoted about a post 19 mounted onthe top plate 20 of the holder. A segment gear 21 on the end of arm 15meshes with a gear 22 attached to the adjusting shaft 23 which extendsfrom rotary potentiometer 17. Gear 22 and segment gear 21 are sized sothat the adjusting shaft 23 of the potentiometer is rotated throughapproximately 220 as the pivoted arm 15 rotates from the positioncorresponding to the largest cassette for which the holder is designedto the position corresponding to the smallest anticipated cassette.

One potentiometer that has been found satisfactory for use with thisarrangement is Spectrol Electronics Corporation s Model 140, which hasan electrical range of 250 and a resolution percentage of 0.255 percent.Thus, in a 220 arc, this potentiometer provides approximately 300adjusting steps. When this potentiometer is used in connection withstandard X-ray beam adjusting equipment the individual steps in theadjustment of the beam are too small to be noticeable. Thus, in effectthe system, and the potentiometer, are continuously variable.

FIG. 1 illustrates in phantom the positions of the pivoted armcorresponding to the smallest and largest cassettes. The post 19 aboutwhich the arm is pivoted is located intermediate a line A defined by theside of the largest cassette and a line B defined by the side of thesmallest cassette. This is done to make the relationship between thecassette size and the potentiometer setting as nearly linear aspossible. In order to faciliate precise adjustment of the X-ray beam tothe exact size of any cassette, it would be preferable to have a linearrelationship between the cassette size and the potentiometer setting.With a pivoted arm, this relationship is not precisly linear because theposition of the arm, and thus the potentiometer setting, are linearlyrelated to the sine of the angle formed by the side of cassette l3 and aline from the point of contact between arm 15 and cassette 13 throughpivot post 19. In order to keep this angle at a minimum, pivot post 19is preferably positioned substantially equi-distant between the line Adefined by the side of the largest cassette and the line B defined bythe side of the smallest cassette.

Another step taken to keep the relationship between the cassette widthand the potentiometer setting as nearly linear as possible is the use ofan offset pivoted arm. As seen in FIG. 1, arm 15 is offset to provideclearance for the larger cassettes. As a result, the end of the armcontacts all sizes of cassettes, which keeps the distance from the pivotpoint to the point of contact with the cassette substantially constantand thereby helps minimize deviation from linearity.

In order to facilitate insertion of a cassette into the holder, meansare provided for pivoting arm 15 away from the cassette when the holderis removed from the X-ray table. As shown in FIGS. 2 and 3, a spring 24is attached to the pivoted arm 15 and to a pivoted stop 25. The springbiases the pivoted arm towards the stop. However, rotation of the arm inthis direction is limited by a block 26, attached to the pivoted arm 15,which contacts the pivoted stop 25. Stop 25 is pivoted about a post 27mounted on the top plate 20 of the holder. A second spring 28 attachedto the stop 25 and to a bracket 56 secured to the top plate 20 of theholder tends to rotate the stop 25 clockwise. As a result, when theholder is removed from the table, stop 25 rotates clockwise and contactsthe block 26 on the pivoted arm, thereby rotating the pivoted arm 15clockwise toward the side of the holder. As a result, the arm does notinterfere with the changing of cassettes.

When the holder is inserted in the table, a post 29 on the table (shownin phantom) hits stop 25 and rotates it counterclockwise. A guide 30 isprovided to facilitate alignment of the holder with the post on thetable. The arm 15 rotates counterclockwise with the pivoted stop 25until the end of the arm 15 contacts the cassette, at which point thearm stops. If there is no cassette in the holder, the arm continues torotate with the stop. This operates a safety switch 31 that prevents theX-ray tube (not shown) from being activated when there is no cassette inthe holder.

The switch 31 is operated by a disk 32 mounted on the adjusting shaft 23of the rotary potentiometer 17. A roller level actuator 33 on switch 31rides on the rim of this disk. When a holder is inserted in the tablewithout a cassette in it and the arm pivots all the way with the stop,the roller drops into a notch 34 on the rim of the disk. This opens theswitch, thereby deactivating the X-ray tube and preventing accidentalexposures without a cassette. The position in which the notch 34 on disk32 stops when the arm is pivoted all the way can be adjusted byadjusting the position of the block 26 on the pivoted arm. As best seenin FIG. 3, block 26 is mounted on the pivoted arm by a pair of screws35, 36. One of the screws 36 extends through an enlarged hole 37 in thearm which permits adjustment of the position of the block on the arm.

As was mentioned above, the length of the cassette in the holder issensed by a second rotary potentiometer 18 connected through gearingmeans and a cable 16 to the rear centering jaw 12. Referring to FIGS. 2and 4, from the jaw the cable passes around an idler pully 38 and onto arotary drum 39 to which the other end 40 of the cable is attached. Agear 41 on top of drum 39 meshes with a gear 42 mounted on the adjustingshaft 43 of the rotary potentiometer 18, which is held in place by abracket 44 to the top plate 20 of the holder. As best seen in FIG. 4,gear 42 is attached to the adjusting shaft 43 through a screw 45 whichcloses a horizontal slot 46 in the hub 47 of gear 42 and thereby deformsthe bore 48 through which the adjusting shaft 43 passes.

The cable -16 from the centering jaw 12 to the rotary drum 39 is kepttaut by. a spring 49 and a second cable 50, attached to spring 49, whichextends around the hub 47 of the gear 42 on the adjusting shaft of thepotentiometer. The other end 51 of this cable is secured in a radialslot 52 in the gear. The cable and spring tend to rotate gear 42counter-clockwise, which rotates the rotary drum clockwise and keepsslack out of the cable 16 connected to the rear centering jaw.

The gear 41 on the rotary drum and the gear 42 attached to the shaft ofthe potentiometer are sized so that the adjusting shaft 43 is rotatedthrough approximately 220 as the rear centering jaw moves through itsrange of travel. As a result, the same type of potentiometer can be usedfor sensing the length as is used for sensing the width of the cassette.

The two potentiometers 17, 18 and the no-cassette sensing switch 31 areconnected to an eight contact plug 53 mounted on the rear of the holder.When the holder is inserted in an X-ray table, the plug makes contactwith the prongs 54 of a male connector (shown in phantom in FIG. 2) onthe table. This connects the potentiometers to a system (not shown) forcontrolling the size of a X-ray beam and connects the safety switch tothe controls (not shown) for energizing the X-ray tube.

The holder described above may be used with a number of conventionalX-ray beam size limiting systems in order to adjust the beam size tocorrespond to any cassette, standard or nonstandard, within the range ofms sette sizes that the holder is designated to accommodate. Thus, thisholder provides much greater flexibility than any previous system forautomatically adjusting the X-ray beam size and also minimizes thenumber of connections that must be made to the holder. Of course, theholder described above is but one example of many possible embodimentsof our invention and many modifications may be made to this holderwithin the scope of this invention, which is defined by the appendedclaims.

We claim:

I. A size sensing X-ray cassette holder comprising:

a. means for centering a cassette in the holder;

b. an arm pivoted about a point intermediate a first line defined by theside of the largest cassette the holder is designed to be used with anda second line defined by the side of the smallest cassette the holder isdesigned to be used with, said arm having a free end adapted to contacta side of the cassette;

c. a continuously variable transducer, means for adjusting thetransducer; and

d. means for connecting the pivoted arm to the transducer adjustingmeans, whereby the transducer is automatically adjusted as the armpivots.

2. A holder according to claim 1 wherein the means for centering thecassette comprises a pair of jaws, further comprising:

a. a second continuously variable transducer, means for adjusting saidsecond transducer; and

b. means for connecting one of the centering jaws to the means foradjusting said second transducer, whereby said second transducer isautomatically adjusted as the jaws are moved to grip the cassette.

3. A holder according to claim 2 wherein:

a. the second transducer is a rotary potentiometer;

b. the means for adjusting the potentiometer comprises a rotary shaftextending from the potentiometer; and

c. the means for connecting the centering jaw to the rotary shaft of thepotentiometer comprises a cable attached to the centering jaw and gearmeans connecting the cable to the rotary shaft of the potentiometer.

4. A holder according to claim 1 wherein:

'a. the transducer is a rotary potentiometer;

b. the means for adjusting the potentiometer comprises a rotary shaftextending from the potentiometer; and

c. the means for connecting the pivoted arm to the shaft comprises asegment gear on the pivoted arm and a gear attached to the adjustingshaft.

5. A holder according to claim 1 wherein the arm pivots about a postmounted substantially equi-distant between said first line and saidsecond line.

6. A holder according to claim 1 wherein said arm is offset to provideclearance for said largest cassette.

7. A size sensing X-ray cassette holder comprising:

a. a pair of jaws adapted to center a cassette inserted in the holder;

b. a continuously variable transducer having a rotary adjusting shaftextending therefrom; and

c. a cable having one end attached to one of the centering jaws and theother end attached to a rotary drum, and gearing means connecting thedrum to the rotary adjusting shaft, whereby the transducer isautomatically adjusted as the jaws are moved to grip the cassette.

8. A holder according to claim 7 wherein the transducer is a rotarypotentiometer. t

9. A holder according to claim 8 wherein the gearing means includes agear mounted on said adjusting shaft and the holder further comprisesbiasing means connected to the gear on the adjusting shaft adapted torotate said gear and thereby take up slack in said cable.

10. A holder according to claim 8 wherein said gearing means comprises agear on the rotary drum that meshes with a gear on the adjusting shaftof the potentiometer.

11. In a size sensing x-ray cassette holder having a pivoted arm adaptedto contact a side of a cassette mounted in the holder; the improvementcomprising:

a. a pivoted stop adapted to pivot independently of said pivoted arm andto contact the arm and limit the movement of the arm;

b. a first spring tending to rotate the stop in a first direction andthereby move the pivoted arm away from the cassette;

c. said pivoted stop being adapted for rotation in a direction oppositeto said first direction by a projecting member on an X-ray system whenthe holder is inserted in the X-ray system, whereby said pivoted arm isfree to rotate towards the cassette;

and

d. a second spring urging the pivoted arm towards the pivoted stop,whereby when the holder is inserted into the X-ray system the arm pivotswith the stop until the arm contacts the side of the cassette.

1. A size sensing X-ray cassette holder comprising: a. means forcentering a cassette in the holder; b. an arm pivoted about a pointintermediate a first line defined by the side of the largest cassettethe holder is designed to be used with and a second line defined by theside of the smallest cassette the holder is designed to be used with,said arm having a free end adapted to contact a side of the cassette; c.a continuously variable transducer, means for adjusting the transducer;and d. means for connecting the pivoted arm to the transducer adjustingmeans, whereby the transducer is automatically adjusted as the armpivots.
 2. A holder according to claim 1 wherein the means for centeringthe cassette comprises a pair of jaws, further comprising: a. a secondcontinuously variable transducer, means for adjusting said secondtransducer; and b. means for connecting one of the centering jaws to themeans for adjusting said second transducer, whereby said secondtransducer is automatically adjusted as the jaws are moved to grip thecassette.
 3. A holder according to claim 2 wherein: a. the secondtransducer is a rotary potentiometer; b. the means for adjusting thepotentiometer comprises a rotary shaft extending from the potentiometer;and c. the means for connecting the centering jaw to the rotary shaft ofthe potentiometer comprises a cable attached to the centering jaw andgear means connecting the cable to the rotary shaft of thepotentiometer.
 4. A holder according to claim 1 wherein: a. thetransducer is a rotary potentiometer; b. the means for adjusting thepotentiometer comprises a rotary shaft extending from the potentiometer;and c. the means for connecting the pivoted arm to the shaft comprises asegment gear on the pivoted arm and a gear attached to the adjustingshaft.
 5. A holder according to claim 1 wherein the arm pivots about apost mounted substantially equi-distant between said first line and saidsecond line.
 6. A holder according to claim 1 wherein said arm is offsetto provide clearance for said largest cassette.
 7. A size sensing X-raycassette holder comprising: a. a pair of jaws adapted to center acassette inserted in the holder; b. a continuously variable transducerhaving a rotary adjusting shaft extending therefrom; and c. a cablehaving one end attached to one of the centering jaws and the other endattached to a rotary drum, and gearing means connecting the drum to therotary adjusting shaft, whereby the transducer is automatically adjustedas the jaws are moved to grip the cassette.
 8. A holder according toclaim 7 wherein the transducer is a rotary potentiometer.
 9. A holderaccording to claim 8 wherein the gearing means includes a gear mountedon said adjusting shaft and the holder further comprises biasing meansconnected to the gear on the adjusting shaft adapted to rotate said gearand thereby take up slack in said cable.
 10. A holder according to claim8 wherein said gearing means comprises a gear on the rotary drum thatmeshes with a gear on the adjusting shaft of the potentiometer.
 11. In asize sensing x-ray cassette holder having a pivoted arm adapted tocontact a side of a cassette mounted in the holder; the improvementcomprising: a. a pivoted stop adapted to pivot independently of saidpivoted arm and to contact the arm and limit the movement of the arm; b.a first spring tending to rotate the stop in a first direction andthereby move the pivoted arm away from the cassette; c. said pivotedstop being adapted for rotation in a direction opposite to said firstdirection by a projecting member on an X-ray system when the holder isinserted in the X-ray system, whereby said pivoted arm is free to rotatetowards the cassette; and d. a second spring urging the pivoted armtowards the pivoted stop, whereby when the holder is inserted into theX-ray system the arm pivots with the stop until the arm contacts theside of the cassette.